What is this bolt for:

[laxman21]

Just to the left of the ERG valve, square head, bolt/plug

[oldblu65]

That appears to be a pipe plug . They always have a square head . Is that on some part of the cooling system ?

[goser]

I think I remember reading in one of the intake manifold threads that older generations had the coolant temperature sensor there.

[Rick Norwood]

It is indeed a caped off port into the cooling system, and it is a Pipe Plug. The thermostat housing is directly above it.

[laxman21]

Originally Posted by Rick Norwood

It is indeed a caped off port into the cooling system, and it is a Pipe Plug. The thermostat housing is directly above it.

What threads does the bolt use? just want to see if I can put a temp sensor in there.

[Rick Norwood]

I will look on my scrap manifold this afternoon and post back. In all probability, it is a 1/2 inch tapered pipe thread (NPT).

[Rick Norwood]

O.K. Sorry I didn't respond last night. I looked at my scrap manifold and tried a 1/2 in pipe, but it was too big. I looked through all of my junk but had nothing that would fit. So, I went to Home Depot and bought a 3/8 Pipe plug and it screwed right in. So to answer your question, the hole has a 3/8-18 Pipe thread.

Oh and BTW you owe me $1.57 for the plug. LOL.

[laxman21]

Originally Posted by Rick Norwood

O.K. Sorry I didn't respond last night. I looked at my scrap manifold and tried a 1/2 in pipe, but it was too big. I looked through all of my junk but had nothing that would fit. So, I went to Home Depot and bought a 3/8 Pipe plug and it screwed right in. So to answer your question, the hole has a 3/8-18 Pipe thread.

Oh and BTW you owe me $1.57 for the plug. LOL.

Thanks. My 99 Burb has the same port with a sensor in it.

[blazes9395]

That plug was used, on some models, for a temperature sensor. I just don't remember which models...

[laxman21]

That plug is in there tight. Couldn't get it to budge.